KT&C/Dahua setup with a ground loop?

[tms233 0]

Sorry if this is a little long but I hope somebody can help.

 

I have read posts on ground loops and hum bars, and several articles on the web, but I still can't figure out what is going on here. I have a faint concept of electricity and ground loops, and this issue has held me up for a week now.

 

I have two outdoor KT&C KPC-N701's (960H Bullet, IR, TDN, 2x12mm, 12vdc/24vac) mounted on the inner wood facia of my house eve's, connected to quality RG59 siamese (bare copper core, 95% braid, 18/2 copper etc) using compression connectors, running through my attic, down into a wall, then splitting off to an Altronix altv1224C supply (16 channel Dual voltage 12vdc/24vac), and an Dahua (Dahua) Hybrid DVR. This setup was greatly influenced by the people posting on this site, thanks folks.

 

So, I wire both cameras to the DC side of the power panel and it all looks pretty good. If I have one camera wired to the DC side, it looks good. If I have one camera wired to the AC side, it works good. BUT, when I move both cameras to the AC side, or one on DC and one on AC, I get the horizontal "hum bars" moving from bottom to top, and the quality of the picture seems to degrade.

 

All the hardware is great in case anybody is wondering. I will post shots with some details as soon as I make it over this hump. I have 2 more coax cables included in this run but the cameras aren't mounted.

 

I made sure to hang the cables in the attic away from the romex power wire, lamps, metal etc. The closest they come to one power wire at one location is about a foot, and it is at a 90 degree angle. I monitor everything on a computer monitor using a monitor switch (which works great) between the dvr and computer. The monitor is the only thing that isn't fresh out of the box. The monitor, DVR and switch are all plugged into the same surge protector going in to one outlet. The power panel is plugged directly into a different outlet, but in the same room.

 

Everything I read says it's an AC ground loop issue?? Great, but how. The more I read, the more it makes less sense. I can't see any indication my cameras are touching metal and giving me my second ground, if that is in fact the problem. Unless there's some mysterious cut in a cable in one of the 60 foot runs, I'm not sure where the problem is. My longest runs will be 60 to 70 feet with the KT&C 701's which draw nearly 1 amp. Those I wanted on the AC. My other analog cameras are shorter runs covering smaller areas and draw about 1/3 the power (KT&C 501's). Those I wanted on the DC side.

 

I have a multimeter, but still learning how to use it and haven't quite figured out how to use it for this situation. I use my laptop on the network to view and make adjustments at the camera location, but I don't have an independent monitor I can hook up to the camera. I'll buy a test monitor if I really have to but dang $$, I'd rather not unless absolutely necessary.

 

Articles on the web about ground loops don't make sense to me.. "measure between any two shields of the video cables..". How do you measure "between TWO shields"?? I understand what the cable shield is, but where would the probles go? And what should the numbers show? There's an article showing you where to put the probes, on a VCR. Yeah, a VCR looks nothing like the options I have on the back of my Dahua Hybrid. My own ignorance in this situation cracks me up.

 

I am adding two more analog and one IP camera to this setup, but I didn't want to go a step further until I figure this issue out. But I was thinking of hooking up cameras to the other two wired locations just to see if the problem exists. If anybody can and wants to throw some input or guidance in, it would be greatly appreciated. I'm sure I'm leaving some pertinent information out of this long story.

[jeromephone 6]

A cheap way to test would be to get 2 wall wart power supplies and power up the cameras one at a time and then together. If that works the problem may be in the power supply itself.

[tms233 0]

That's true. Completely isolating them from my power panel with everything else staying the same would check another cause off the list. I'd forgotten about that option in all the confusion. Thanks for the response.